The present invention relates to the production of poly(ester carbonate) polymers by a two phase reaction system.
Polycarbonates are conventionally prepared from a difunctional phenol such as 2,2-bis(4-hydroxyphenol) propane (commonly referred to as bisphenol-A) and phosgene by either a solution process or an interfacial process. Briefly the solution process involves reacting phosgene with the difunctional phenol in a single organic phase employing a compatible solvent such as dichloromethane and having a base such as pyridine to accept by-product hydrogen chloride. Such a solution process is described, for example, in U.S. Pat. No. 3,028,365 to Schnell et al. (Apr. 3, 1962). In the interfacial process, the difunctional phenol is introduced as a diphenolate, particularly of an alkali hydroxide (represented by the disodium phenolate of bisphenol-A) in an aqueous phase and mixed with the phosgene (neat or in an organic solvent such as dichloromethane) to form an emulsion. A phase transfer catalyst (that is an acid acceptor) such as triethylamine may be used to accept the by-product hydrogen chloride from the condensation in the organic phase and to transfer the hydrogen chloride to the basic aqueous phase where it is neutralized and the catalyst is regenerated in its basic form to accept additional hydrogen chloride. Alternatively other types of catalysts such as quaternary ammonium salts such as chlorides may be used. Additionally, chain length regulators such as t-butylphenol may be employed to limit the molecular weight and thus the viscosity of the polymer. Examples of such a process are described in U.S. Pat. No. 3,646,102 to Kobayashi et al. (Feb. 29, 1972) and in P. W. Morgan, Condensation Polymers: By Interfacial and Solution Methods (Interscience 1965). Similar interfacial processes for the formation of polyesters from bisphenol-A and acyl halides such as terephthaloyl chloride or isophthaloyl chloride are described by W. M. Eareckson in J. Polymer Science, Vol. 40, pp. 399-406 (1959) and in Morgan, pp. 325-93. Other suitable bifunctional phenols for such polyesters are described in British Pat. No. 897,640 to Imperial Chemical Industries Limited (May 30, 1962) and Morgan, pp 334-337. Other suitable acyl chlorides are described, for example, in U.S. Pat. No. 3,028,364 to Conix et al. (April 1962), U.S. Pat. No. 4,137,218 to Prevorsek et al. (Jan. 30, 1979) and in Morgan, pp 334-337.
A class of polymers has been developed from polyfunctional phenols such as bisphenol A, polyfunctional carboxylic acids or preferably their acyl halides and phosgene. These polymers are referred to as poly(ester carbonate) polymers and are broadly described, for example, in U.S. Pat. No. 3,169,121 to Goldberg (Feb. 9, 1965) and more especially disclosed in German Patent Application DOS No. 2,714,544 (published Oct. 2, 1977) (which corresponds to pending U.S. Patent Application Ser. No. 764,623 of Prevorsek et al., filed Feb. 1, 1977), now U.S. Pat. No. 4,156,069. Also pertinent are three articles by Kolesnikov et al. published in Vysokomol. Soyed. as, respectively, A9: No. 5, pp. 1012-1015 (1967) A9; No. 7, pp. 1520-1524 (1967); and A10: No. 1, pp. 145-151 (1968). In general, the above published German Patent Application describes poly(ester carbonate) polymers having a desirable combination of melt processibility, high glass transition temperature, high molecular weight as indicated by specific viscosities in the general range of 0.5 to 1 as measured in solvents such as methylene chloride or tetrachloroethane and high Izod impact resistance. By contrast, the poly(ester carbonate) polymers disclosed in the Kolesnikov et al. articles are generally of lower glass transition temperature and lower specific viscosity rendering them unsuitable for many of the intended uses, especially as tough, impact resistant plastic articles. The particular poly(ester carbonates) from terephthalic acid prepared following the Examples of the Goldberg patent, and particularly Example 5, had been determined experimentally, when molded into standard test specimens, to have relatively poor values for melt stability, glass transition temperature, impact strength and haze as compared to the products of the Prevorsek et al. U.S. Pat. No. 4,156,069 and corresponding DOS No. 2,714,544.
Interfacial processes for producing polyesters and polycarbonates offer significant advantages over solution processes including lower cost of neutralization of byproduct acid halide, faster reaction and elimination of noxious organic bases. It would be desirable to be able to prepare poly(ester carbonate) polymers of the type described in the above referenced published German Patent Application by an interfacial process. The Kolesnikov et al. articles employ such an interfacial process, but without achieving the desired combination of properties. Similarly, as indicated in Comparative Example 3 herein, the teachings of U.S. Pat. No. 3,646,102 to Kobayashi et al. can be combined with the teachings of published German Patent Application No. 2,714,544. One would form short polyester oligomers as in DOS No. 2,714,544 and then add phosgene as in DOS No. 2,714,544, but would perform both steps in an interfacial process with very high agitation as in U.S. Pat. No. 3,646,102. A process combining these two references in this manner produces poly(ester carbonate) polymers inferior to the polymers of the published German Patent Application. Because of the difficulty of phase separation of the aqueous and organic phases inherently present in an interfacial polymerization, these polymers have poor color, haze values, glass transition temperatures and other poor properties. It is expected that, under conditions in which the product quality is even moderately good, the yields are likely to be low, because poor phase separation leads to difficulties in washing, isolating and recovering the polymer.
Accordingly it is an object of the present invention to produce poly(ester carbonate) polymers having the combination of properties described in German Patent Application No. 2,714,544, including all of the above features, by interfacial process in good yields.